Long before the earth knew pollutants of any kind, a huge, ancient sea covered. Pure, natural salt was the main ingredient of this sea, and over millions of years, the water evaporated, leaving the salt in undisturbed deposits. At some point during the earth's Jurassic era, a range of volcanos erupted around the ancient sea bed, sealing the salt with layers of thick volcanic ash, protecting these precious deposits against the pollution that man would eventually introduce into the environment. Near...